Quality-by-design optimized reversed phase-high performance liquid chromatography method for quantification of...

Everolimus, a potent mTORC1 inhibitor used in various oncological and immunological indications, requires precise quantitative analysis due to its narrow therapeutic window and susceptibility to pharmacokinetic variability. This study aimed to develop and validate a robust, sensitive, and cost-effective reverse-phase high-performance liquid chromatography method for EVR quantification in bulk drugs, marketed formulations, and nanoparticle-based delivery systems. A systematic analytical Quality by Design approach was utilized to facilitate method development and ensure method optimization. Critical method variables were identified through one-factor-at-a-time screening and subsequently optimized using a Box-Behnken Design. Thirty-seven experimental runs were evaluated to model their effects on retention time, tailing factor, theoretical plates, and peak area. The QbD-optimized chromatographic conditions, 85% ACN and 15% water, 0.85 mL/min flow rate, 50 °C column temperature, and 20 µL injection volume, detection wavelength was 278 nm yielded a high composite desirability (0.759) and produced sharp, well-resolved EVR peaks. Method validation was performed in accordance with ICH Q2(R2) guidelines, and results were found within the accepted limits. Linearity range was found to be from 100 ng/mL to 10,000 ng/mL, the coefficient of determination was 0.9965, and LOD and LOQ was found to be 50 ng/mL and 100 ng/mL, respectively. Overall, the developed RP-HPLC method is sensitive, reproducible, and suitable for routine quantification of EVR in pharmaceutical formulations and nanoformulations, providing a practical alternative to liquid chromatography with tandem mass spectrometry in resource-limited analytical settings.